The physiology of human muscles contracts in three distinct fashions. The first is by concentric or “positive” contraction in which the muscle encounters an external load that is light enough to enable the muscle to shorten while contracting. The second is for the muscle to encounter an external load that is too heavy for the contracting muscle to shorten against thus producing a static or “isometric” contraction producing no movement. The third is by an eccentric or “negative” contraction in which a muscle encounters an external load that is heavy enough to cause a lengthening of the muscle under contraction. It is a well-established and accepted fact among the medical and rehabilitation professions that muscles can produce force at a much higher magnitude in an isometric or static contraction versus a concentric or positive contraction. Also, muscles produce their highest levels of force during the performance of an eccentric or negative contraction. Since muscular strength increases in direct proportion to the amount of tension imposed upon the muscles, physiologists have proven conclusively that strength is produced to a much higher level and in less time with eccentric contractions versus conventional concentric and static contractions.
Furthermore, muscles achieve this higher level of force during eccentric contractions much more efficiently than during a comparable load under concentric contractions. This physiological fact has led to the realization among the medical profession that people who are neurologically impaired because of injury or surgery can still be rehabilitated back to health by eccentric contractions despite the fact that they are unable to perform concentric contractions. Numerous studies also show that the elderly population can achieve increased health benefits such as increased muscular strength and balance and can reduce the chance of injuries from falls. These benefits can be achieved despite the possibility of suffering from age or disease related cardiovascular and pulmonary conditions. Eccentric contractions produce the much desired benefits of strength building and injury prevention at a much lower metabolic cost than concentric or static contractions, thus imposing much less demand on the cardiovascular and pulmonary systems of the body. It is therefore an objective of the present invention to provide an apparatus that enables a user to perform eccentric contractions of the muscles.
Various types of equipment have been developed over the years in an attempt to address these concerns; however this equipment has met with little success. These types of equipment range from simple conventional barbells to prohibitively expensive hydraulics. These machines are generally limited to one particular muscle, requiring the purchase of a complete line of individual machines, which can be very expensive financially and can occupy a large amount of space. This also poses a problem with paraplegics as they have to move from one machine to the next, which is virtually impossible without the assistance of one or more therapists or trainers. This often times leads to a feeling of dependence and depression. This is also the cause of many injuries to therapists, trainers and patients alike annually.
With few exceptions, prior art exercise and rehabilitation machines have failed to recognize the obvious problems to be addressed, the differing force generating capabilities during concentric, static, and eccentric contractions. Almost all prior machines impose a single load that limits the ability of muscles to contract with a higher force when generating eccentric contractions because of the inability of the exercising or rehabilitating muscle to shorten under a significantly greater load so that a much stronger lengthening can occur.
Examples of prior devices are plentiful. The Nautilus Co. among others has employed the use of spiral cams in an attempt to accommodate the force curves that take place as muscles lengthen and leverage changes that occur during a concentric contraction. However, these devices have failed to address the much more obvious and important strength differences between concentric, static, and eccentric contractions. Another example of an exercising or rehabilitation machine uses a weight stack sliding vertically on guide rods. The weight on this type of machine can be changed between exercises; however, the weight remains constant during the exercises, severely limiting static and eccentric contractions. Another example of an exercising or rehabilitation machine employs the use of levers. Regardless of the amount of weight put on the machine, it remains constant and does not take into account the fact that muscles contract at three different force levels during any given movement of that muscle. Another example of an exercising or rehabilitation machine is a plate-loaded machine. The weight on this type of device may be changed between exercises. However, the weight remains constant throughout the concentric, static, and eccentric contractions of a particular exercise. There is also the option of traditional barbells. However, not only are barbells incapable of changing the amount of weight applied to the muscles in concentric, static, and eccentric contractions, they are in fact quite dangerous to all involved.
In view of the foregoing, there is a need for improved techniques for providing an exercising and rehabilitation apparatus that takes into account the differing force generating capabilities during concentric, static, and eccentric muscular contractions and is capable of producing and measuring 0-100% of maximum voluntary eccentric, concentric, and static muscular contractions of an individual while exercising or rehabilitating.
Unless otherwise indicated illustrations in the figures are not necessarily drawn to scale.